This invention relates in general to microvalve devices and in particular to a microvalve device having a check valve.
The term "microvalve device", as used in this application, means a device that includes a microvalve. The term "microvalve", as used in this application, means a valve having features with sizes in the micrometer range formed at least partially by micromachining techniques. Typical micromachining techniques include conventional computer chip fabrication techniques (such as chemical etching). It should be appreciated that a microvalve device may include other components in addition to a microvalve. These additional components may be micromachined components or standard sized (larger) components.
Microvalve devices may offer significant packaging and cost advantages.
A check valve is a valve that permits fluid flow in a first direction (from an inlet port of the valve to an outlet port of the valve) and prevents fluid flow in a second direction (from the out let port to the inlet port). Generally, a check valve device has a body with a chamber defined therein. The chamber has an inlet port and an outlet port for providing fluid communication through the body to the chamber. A check valve is disposed in the chamber for movement between a closed position and a fully open position. In operation, when the fluid pressure of a first fluid source connected to the inlet port is greater than the fluid pressure of a second fluid source connected to the outlet port, the check valve is forced by the differential fluid pressure of the fluid acting across the check valve to the fully opened position. When the check valve is not in the closed position, fluid is allowed to flow from the inlet port to the outlet port through the chamber. When the fluid pressure of the first fluid source is less than the fluid pressure of the second fluid source, the check valve is forced by the differential fluid pressure acting across the check valve to move to the closed position. When moved to the closed position, the check valve restricts fluid from flowing between the inlet and outlet ports. Occasionally, a check valve device will also include an override actuator by means of which a check valve can be positioned to a position other than that to which the differential fluid pressure is urging the check valve.
An objective of this invention is to provide the function of a check valve in a microvalve device.